I. Field of the Invention
This invention relates to aromatic antioxidants in general and in particular to aromatic diamine antioxidants for organic materials.
II. Description of the Prior Art
Various materials including aromatic amines have been suggested for use as antioxidants in organic materials. Among those compounds are those described in U.S. Pat. No. 3,217,040. Also known are various other types of antioxidants such as those described in U.S. Pat. Nos. 4,066,562, 4,104,255, 4,222,883, and 4,222,884.
Some of the compounds of the present invention are known per se for uses in various other fields. In particular, the 3,5-diethyltoluenediamine compounds and the 4,4'-methylene-bis[2,6-diisopropylaniline] of the present invention are known as valuable chain extenders in the formation of polyurethanes, especially in processes known as reaction injection molding "RIM."
The antioxidants of the prior art, however, suffer various disadvantages. Notably, most of the known antioxidants are solids, amorphous, crystalline, or similar structures which are often difficult to dissolve in various organic materials, especially lubricating oils. Additionally, many of the known antioxidants have a very poor solubility in organic materials and additional solubility agents must sometimes be added, thereby detracting from the value of the antioxidant. Volatility problems also prevent the use of some of these compounds. Other antioxidants such as the ortho and para-phenylene diamines are suitable antioxidants in gasoline, for example, but are suspected toxins.